1. Field of the Invention:
The present invention relates to an information indication system, particularly to an information indication system for digitally indicating a continuously varying output such as the output of the measured light in the case of a camera.
2. Description of the Prior Art:
The recent advance in digital techniques has made digital indication in the field of information indication more and more popular. This concept is also applied in the indication of the exposure determining factor in photography and has, to some extent, been used for indicating the photographic information of a camera.
However, photographic information for a camera is indicated only after various kinds of the photographic data have been processed, mainly based upon the quantity of the measured light. Accordingly, indication information naturally varies when some variation takes place in the information of the measured light, such as the brightness of the object to be photographed.
Thus when the indication information is indicated by means of an indication means such as a seven-segmented unit which presents a superior response to the variation of the input information, the indicated value varies in response to the above mentioned continuously varying indication information so that the photographer can not visually follow the variation of the indication value. This is so because the indication value itself varies within a very short period as to leave an after-image. Thus, visually, the indication value flickers so that it is impossible to read out the indication value.
U.S. Pat. No. 3,872,483 and DOLS No. 2,435,903 disclose systems according to which indication is made at a certain determined period by enlarging the sampling period in order to avoid the above mentioned shortcoming. These systems are provided with a light measuring circuit for measuring the brightness of the object to be photographed, and A-D converting means for converting the output of the light measuring circuit into a digital quantity, a digital indication means for indicating the output of the A-D converter and a sampling circuit for actuating the A-D converter at a certain determined period in such a manner that the output of the light measuring circuit is converted into a digital value at a certain determined period and updated at a certain determined period. Accordingly, the analog-digital conversion is not carried out continuously but only at the certain determined period. Thus, even when during the pause of the analog-digital conversion, the output of the light measuring circuit varies abruptly so as to deviate largely from the output of the light measuring circuit when the output is converted into digital value, the output converted already into digital value presents the value obtained before the large variation. Thus, in the case of system for an automatic exposure camera with digital control for determining the exposure automatically by means of the output converted into digital value, the output converted into digital value presents the former value even though, as explained above, during the pause of the analog digital conversion the output of the light measuring circuit has varied. The exposure mechanism then, does not operate in accordance with the actual value of the measured light, and fails to obtain a correct exposure. During the pause of the analog digital conversion the indication itself presents the former value and the present instantaneous value can not be indicated until the output has been converted into a digital value after the certain determined period. Further the photographer who decides the exposure himself can not learn the variation immediately when, as explained above, during the pause of the analog digital conversion the output of the measured light varies widely. To repeat, the photographer is obliged to decide the exposure in accordance with the indication value before variation, setting an incorrect exposure condition. This is again disadvantageous.
Thus, the present invention is intended to offer a digital information indication system without the above mentioned shortcoming in accordance with which system the above mentioned flickering can be avoided while a large variation of the brightness of the object to be photographed from the indicated value within the above mentioned certain determined period is immediately detected so as to update the indication. The system is composed in such a manner that the analog-digital conversion is always carried out for the continuously varying information, the timing of the indication being controlled in such a manner that the output of the A-D converter is sampled at a certain determined period during which period the variation of the indication value can visually be followed. In the case of a variation from the indicated value being more than a certain predetermined value, the indication being varied independently of the above mentioned certain determined period.